Quantitative assessment of intermolecular interactions by atomic force microscopy imaging using copper oxide tips
Quantitative assessment of intermolecular interactions by atomic force microscopy imaging using copper oxide tips
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DOI：
10.1038/s41565-018-0104-4
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发表时间：
2018-05-01
影响因子：
38.3
通讯作者：
Fuchs, Harald
中科院分区：
文献类型：
--
作者：
Moenig, Harry;Amirjalayer, Saeed;Fuchs, Harald
原子力显微镜是一种令人印象深刻的工具，可以直接解析有机化合物的键合结构（1-5）。该方法通常涉及通过附着单个分子或原子（如CO或CO2）对探针末端进行化学钝化（参考文献（1，6 -9））。然而，这些探针颗粒仅弱连接到金属顶点，这导致相当大的动态偏转。这种探针粒子偏转导致明显的图像失真，系统性高估键长，在某些情况下甚至导致虚假的键状对比度特征，从而抑制了可靠的数据解释（8-12）。最近，已经使用了一种替代的尖端钝化方法，其中将尖端略微压入氧化的铜基板中，随后进行对比分析，以验证氧端接的Cu尖端（13-15）。在这里，我们表明，由于共价键结合的配置的终端氧原子，这种氧化铜尖端（CuOx尖端）具有很高的结构稳定性，不仅允许定量测定的个别键长和访问键序效应，而且可靠的分子间键表征。特别是，通过消除以前的灵活的探针粒子的限制，我们能够提供一个不寻常的分子间N-Au-N三中心键确凿的实验证据。此外，我们表明，铜氧尖端允许表征的强度和配置的分子组装内的单个氢键。
Atomic force microscopy is an impressive tool with which to directly resolve the bonding structure of organic compounds(1-5). The methodology usually involves chemical passivation of the probe-tip termination by attaching single molecules or atoms such as CO or Xe (refs (1,6-9)). However, these probe particles are only weakly connected to the metallic apex, which results in considerable dynamic deflection. This probe particle deflection leads to pronounced image distortions, systematic overestimation of bond lengths, and in some cases even spurious bond-like contrast features, thus inhibiting reliable data interpretation(8-12). Recently, an alternative approach to tip passivation has been used in which slightly indenting a tip into oxidized copper substrates and subsequent contrast analysis allows for the verification of an oxygen-terminated Cu tip(13-15). Here we show that, due to the covalently bound configuration of the terminal oxygen atom, this copper oxide tip (CuOx tip) has a high structural stability, allowing not only a quantitative determination of individual bond lengths and access to bond order effects, but also reliable intermolecular bond characterization. In particular, by removing the previous limitations of flexible probe particles, we are able to provide conclusive experimental evidence for an unusual intermolecular N-Au-N three-centre bond. Furthermore, we demonstrate that CuOx tips allow the characterization of the strength and configuration of individual hydrogen bonds within a molecular assembly.